MIPS: CPS: Set Status.KX on entry for MIPS64 kernels

MIPS: CPS: Set Status.KX on entry for MIPS64 kernels

If the kernel may make use of 64 bit addresses outside of the
compatibility address space then we need to set KX such that those
accesses can succeed. Do so for MIPS64 kernels.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/11201/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>